This invention relates generally to the field of conjugated polymers, and more particularly relates to a novel class of conjugated electroluminescent polymers useful as semiconductive materials in electroluminescence devices and the like.
xe2x80x9cConjugatedxe2x80x9d polymers are polymers containing a xcfx80-electron conjugated system along the main chain (or xe2x80x9cbackbonexe2x80x9d), and have been known for some time to have utility as organic semiconducting materials. See, e.g., Organic Conductors, ch. 11, J. P. Farger, Ed. (New York, N.Y.: Marcel Dekker, 1994). Conjugated polymers include, for example, cis and trans polyacetylenes, polydiacetylenes, polyparaphenylenes, polypyrroles, polythiophenes, polybithiophenes, polyisothianaphthene, polyphenylenevinylenes, polythienylvinylenes, polyphenylenesulfide, and polyaniline. More recently, conjugated polymers have also been discovered to be useful as electroluminescent materials, i.e., as materials that emit light when excited by application of an electric current (Burroughs et al. (1990) Nature 347:539-541; May (1995) Phys. World 8(3):52-57). Accordingly, these polymers have been proposed for use in a variety of applications. For example, conjugated polymers may be used as the active material in semiconductor thin film devices such as light-emitting diodes (LEDs), transistors, photodetectors and solar cells. Conjugated polymers may also be used in electrochemical devices such as rechargeable batteries and light emitting electrochemical cells (both as thin films and in solution), as electrochemical sensors, and as electrical conductors (after being heavily doped).
The most promising application for conjugated polymers is in electroluminescent displays. Red, green, and blue emissions from conjugated polymers have all been demonstrated. Currently, red and green polymer LEDs are sufficiently bright, efficient, and stable for a number of display applications, whereas blue polymer LEDs lag in power efficiency and lifetime. Blue light emitting polymers are for the most part based on poly(paraphenylene) (PPP) and poly(fluorene), which is itself a type of poly(paraphenylene) except that every two neighboring phenyl rings are locked in one plane. Other blue light emitting polymers include alkoxy-substituted PPP, as disclosed by Yang et al. (1996), xe2x80x9cEfficient Blue Polymer Light-Emitting Diodes from a Series of Soluble Poly(paraphenylene)s,xe2x80x9d J. Appl. Phys. 79(2):934-939. Polyfluorenes with 9,9-dialkyl side groups are currently the best performing blue polymers, and are described, for example, in U.S. Pat. No. 5,900,327 to Pei et al. and U.S. Pat. No. 6,169,163 to Woo et al. Compared to red- and green-emitting polymers, however, blue-emitting polymers still lag in power efficiency (thus requiring a high operating voltage) and lifetime (i.e., the spectrum is not stable and tends to red-shift with time, heat, and operation). The problems stem from the dialkyl side groups, which reduce the polymers"" glass transition temperature. The fluorene rings tend to aggregate, forming intraband defects that cause the color shift toward red.
There is accordingly a need in the art for blue-emitting polymers that have high blue luminescence, decreasing the required operating voltage for a blue polymer LED. Ideal polymers would also be conjugated, semiconductive polymers that are soluble in common organic solvents, particularly those used in semiconductor processing, but nevertheless retain semiconductivity, photoluminescence and electroluminescence efficiency, tensile strength, and thermal, chemical and photochemical stability. It would also be desirable to provide such polymers that may be easily modified so as to emit light in the red and green wavelength ranges.
The present invention is addressed to the aforementioned need in the art, and provides a novel family of conjugated electroluminescent polymers useful in a variety of applications, including fabrication of semiconductor thin film devices (e.g., LEDs, transistors, photodetectors and solar cells) and electrochemical devices (e.g., rechargeable batteries, light-emitting electrochemical cells, and electrochemical sensors).
It is another object of the invention to provide such polymers in the form of electroluminescent amino-substituted conjugated polymers, copolymers, and analogs thereof.
It is another object of the invention to provide such polymers in the form of substituted poly(paraphenylenes).
It is still another object of the invention to provide such polymers wherein the polymers are blue light emitting.
It is an additional object of the invention to provide electroluminescence devices containing a polymer of the invention as the electroluminescent material.
It is a further object of the invention to provide other types of semiconductor thin film devices and electrochemical devices fabricated with a polymer of the invention.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.
In one embodiment, a conjugated electroluminescent polymer is provided containing monomer units having the general structure of formula (I): 
wherein:
Ar1 and Ar2 are independently selected from the group consisting of monocyclic, bicyclic and polycyclic arylene, heteroarylene, substituted arylene and substituted heteroarylene groups;
L is alkylene, alkenylene, substituted alkylene, substituted alkenylene, heteroalkylene, heteroalkenylene, substituted heteroalkylene, substituted heteroalkenylene, arylene, heteroarylene, substituted arylene, substituted heteroarylene, or a combination thereof;
Q is a heteroatom;
m is zero or 1;
p is zero or 1, and q is zero or 1, with the proviso that when p is zero, then q is zero;
x is zero or 1;
Q1 and Q2 are independently selected from the group consisting of H, aryl, heteroaryl, substituted aryl, substituted heteroaryl, alkyl, substituted alkyl, heteroalkyl, and substituted heteroalkyl, and Q3 is selected from the group consisting of alkyl, substituted alkyl, heteroalkyl, and substituted heteroalkyl, with the proviso that when m is 1, Q1 and Q2 are other than H; and
Axe2x88x92 is a negatively charged counterion.
It will be appreciated that given the definitions of Q1, Q2, Q3, m and Axe2x88x92, the polymer may be substituted with a primary amino group, a secondary amino group, a tertiary amino group, or a quaternary amine salt. Diarylamino substituents are preferred (wherein m is zero and Q1 and Q2 are aryl, heteroaryl, substituted aryl, or substituted heteroaryl), with diarylamino-substituted poly(paraphenylenes) and copolymers and analogs thereof particularly preferred.
In a preferred embodiment, the electroluminescent polymers are comprised of monomer units having the structure of formula (II): 
wherein:
L, Q, m, p, q, x, Q1, Q2, Q3 and Axe2x88x92 are as defined above; and
W, X, Y, Z, X1, y1, and Z1 are independently selected from the group consisting of N, CH, and CR1, wherein R1 is xe2x80x94(Q)qxe2x80x94(L)pxe2x80x94N(Q1Q2), xe2x80x94(Q)qxe2x80x94(L)pxe2x80x94N(Q1Q2Q3)+Axe2x88x92, xe2x80x94NO2, sulfo (xe2x80x94SO3H), carboxyl (xe2x80x94COOH), phosphono (xe2x80x94O(PO)(OH)2), sulfonato (xe2x80x94SO2xe2x80x94Oxe2x88x92), carboxylato (xe2x80x94COOxe2x88x92), phosphonato (xe2x80x94P(O)(Oxe2x88x92)2), xe2x80x94CN, halo, C1-C20 hydrocarbyl, substituted C1-C20 hydrocarbyl, heteroatom-containing C1-C20 hydrocarbyl, or substituted heteroatom-containing C1-C20 hydrocarbyl, and further wherein Z and Z1 may be linked to form a cyclic group. When any of W, X, Y, Z, X1, Y1, and Z1 is charged, as in the anionic sulfonato, carboxylato, and phosphonato groups, it will be appreciated that the charged atom or group is associated with a suitable counterion, e.g., a metal cation, the ammonium ion xe2x80x94NH4+, or the like.
In another embodiment, a copolymer is provided comprising at least one first monomer unit having the structure of formula (I), preferably having the structure of formula (II), and at least one second monomer unit comprised of a vinylene unit or a monocyclic, bicyclic, or polycyclic arylene, heteroarylene, substituted arylene or substituted heteroarylene unit. The copolymer may be a alternating copolymer, a random copolymer, or an alternating copolymer.
In a further embodiment, electroluminescence devices are provided that contain a polymer of the invention as the electroluminescent material. In some embodiments, it is desirable to incorporate phosphorescent dyes or other additives into the polymer for use in electroluminescence devices. These devices include light-emitting diodes (LEDs), photodetector devices, and light-emitting electrochemical cells. In a particularly preferred embodiment, an electroluminescence device prepared with a polymer of the invention is a cavity-emission electroluminescence device.
In an additional embodiment, other types of devices are provided that are fabricated with a polymer of the invention, particularly photovoltaic devices used for the generation of electrical power, electrochemical sensors used for detecting and/or quantitating chemical and/or biological materials, and transistors, e.g., field-effect transistors (FETs).